p235w11_practice_exam_3_2_sol

The waves described in a b c and e all travel to the

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Unformatted text preview: d and f travel to the left. Note that d and f are almost the same, differing only by a phase shift. Any of the combinations a+d, a+f, b+d, b+f would work. 8: (5 points) Standing waves are often produced in “cavities” like on a guitar string. Explain why this is. a: (3 points) What is required to produce standing waves and how is that condition met inside such cavities? Standing waves are produced when otherwise identical waves travel in opposite directions. This condition is met in cavities when a wave started in the cavity reflects back and forth off the boundaries, creating counter-propagating identical waves of just the kind required. b: (2 points) Why can oscillations of certain wavelengths exist on the string with large amplitude while others cannot? Waves which require a large amplitude oscillation at the ends of the string (which are fixed in place) will rapidly lose any energy which they have, transferring it into the frame which holds the string. As a result, the only waves which will remain at large amplitude are those which have zero amplitude at the locations where the string is fixed. These have = 2L/n. 9. (5 points) Monochromatic light with a wavelength of 450 nm passes through a single narrow slit. On a screen 1.5 m away it produces the diffraction pattern shown below. What is the width of the slit? a. b. c. d. e. *35 m 4.2 m 93 nm 1.8 m...
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